Having worked with both, I think it's really much more about having someone (a team) dedicated to dev experience, maintaining good onboarding tooling, CI/CD, build infrastructure, security configurations, SOP's around package repositories, container image registries, static code analysis tooling, and the works. If you have 2000 repos but finding what you need is easy, then the number itself is not an issue. If you have 1 repo and running unit tests for a small component before merging takes 8 hours, again the number of repos is probably not the issue.